The present invention relates to a simulator system, and in particular to a simulator system which is suitable for use in a flight simulator.
Flight simulators comprise a viewing station which is occupied by a user of the simulator, the appearance of the viewing station to an occupant being a facsimile of the interior of an aircraft cockpit. The viewing station is mounted on a support frame which is displaceable to simulate in-flight motion. The support frame also supports a visual display assembly arranged to present an image to be viewed on a display surface which is visible from a predetermined eyepoint within the viewing station. Typically, the visual display assembly comprises a back projection screen, a projector positioned to project an image onto the back projection screen, and a concave mirror in which a reflection of the back projection screen is viewed from the predetermined eyepoint through a window defined by the structure of the viewing station. The mirror can be of the order of two meters high and thus defines a relatively large surface area. It is difficult to illuminate the back projection screen with sufficient intensity to provide adequate brightness in the reflection of the back projection screen which is viewed in the mirror.
Flight simulators which are used for simulating take off or landing are used in circumstances in which most of the visually significant image information appears in the lower portion of the view through the viewing station window. Thus it is known to arrange the visual display assembly such that the reflection of the back projection screen occupies only a lower portion of the image viewed through the window, the upper portion being occupied by a "background" display. For some applications however this approach is not acceptable, for example in a simulator for use in in-flight refuelling training. During in-flight refuelling, the aircraft being refuelled must be accurately positioned slightly behind and slightly below a tanker aircraft and as a result the visually significant information occupies upper portions only of the view from the eyepoint through the viewing station windows. Accordingly, in simulators which must be capable of simulating a full refuelling mission including take off, refuelling and landing, it is not possible to maintain an acceptable level of brightness in the significant portions of the viewed scene by arranging the visual display assembly such that the reflection of the back projection screen occupies only a portion of the view from the eyepoint through the viewing station windows. Accordingly in such applications it has been conventional practice to provide a display system with a field of view large enough to satisfy all the requirements, but such an approach requires the use of very large optical components and results in a relatively low brightness low resolution display.
It has been proposed to address the problem outlined above by mounting the viewing station so that it can be displaced relative to the visual display assembly. In this known arrangement, the viewing station is mounted so as to rotate relative to a horizontal axis, rotation of the viewing station adjusting the position of the display surface relative to a viewing window defined by the viewing station. This adjusts the position of the display surface relative to the viewing window when viewed from the predetermined eyepoint, and makes it possible by displacement of the viewing station to appropriately position the visually significant image information relative to the viewing station windows.
Displacement of the viewing station in the known arrangement is difficult to control with sufficient accuracy to avoid the displacement being apparent to an occupant of the viewing station. Firstly, the eyepoint of the viewing station must not move significantly in translation during displacement of the viewing station. Secondly, acceleration of the viewing station relative to the support frame must be miinimised if that acceleration is not to give an occupant of the viewing station false cues. These requirements have proved difficult to achieve with the known arrangement.